What are the relationships between different types of transmitted light?

Transmission measurements involve shining light on a sample and measuring the light transmitted through it. The transmitted light is generally classified as shown in the top figure. A spectrophotometer offers three types of measurements:

• Linear transmission measurements of light that passes straight through the sample
• Diffuse transmission measurements of light that scattered inside the sample when passing through it
• Total transmission measurements of all the light transmitted through the sample.

The characteristics of the measurements and the points to be aware of differ according to the type of transmitted light measured. We prepared a clear glass sample (glass filter) and opaque and translucent sample (opal glass). The bottom left figure shows a photograph of a linear transmitted light sample (blue) and a diffusely transmitted light sample (white). As one can see the glass filter is transparent, whereas the opal glass appears cloudy.